The present invention concerns fluid rail assemblies for fuel injected internal combustion engines. More particularly, the present invention relates to a conveyance of a fluid from a fluid rail assembly to a hydraulically actuated, electronically controlled fuel injector.
Certain fuel injectors can be described as hydraulically actuated, electronically controlled. Hydraulic actuation of the fuel injector is preferably effected by engine oil at an elevated pressure. It should be understood that other fluids self contained in the vehicle powered by the internal combustion engine could also be used for hydraulic actuation of the fuel injector, including brake fluid, power steering fluid, or the like.
An exemplary fuel injector of this type is depicted generally in prior art FIG. 1 at 200. A hydraulically-actuated, electronically-controlled, unit injector (HEUI), of the type described in U.S. Pat. No. 5,181,494 and in SAE Technical Paper Series 930270, HEUIxe2x80x94A New Direction for Diesel Engine Fuel Systems, S. F. Glassey, at al, Mar. 1-5, 1993, which are incorporated herein by reference, as depicted in prior art FIG. 1. HEUI 200 consists of four main components: (1) control valve 202; (2) intensifier 204; (3) nozzle 206; and (4) injector housing 208.
The purpose of the control valve 202 is to initiate and end the injection process. Control valve 202 is comprised of a poppet valve 210, electric control 212 having an armature and solenoid. High pressure actuating oil is supplied to the valve""s lower seat 214 through oil passageway 216. To begin injection, the solenoid of the electric control 212 is energized moving the poppet valve 210 upward the lower seat 214 to the upper seat 218. This action admits high pressure oil to the spring cavity 220 and the passage 222 to the intensifier 204. Injection continues until the electric control 212 solenoid is de-energized and the poppet 210 moves from the upper seat 218 to lower seat 214. Actuating oil and fuel pressure decrease as spent actuating oil is ejected from the injector 200 through the open upper seat oil discharge 224 to the valve cover area of the internal combustion engine, which is at ambient pressure.
The middle segment of the injector 200 consists of the hydraulic intensifier piston 236, the plunger 228, fuel chamber 230, and the plunger return spring 232.
Intensification of the fuel pressure to desired injection pressure levels is accomplished by the ratio of areas between the upper surface 234 of the intensifier piston 236 and the lower surface 238 of the plunger 228, typically about 7:1. The intensification ratio can be tailored to achieve desired injection characteristics. Fuel is admitted to chamber 230 through passageway 240 past check valve 242 from an external fuel supply.
Injection begins as high pressure actuating oil is supplied to the upper surface 234 of the intensifier piston 236 via passageway 222. As the piston 236 and the plunger 228 move downward, the pressure of the fuel in the chamber 230 below the plunger 228 rises. High pressure fuel then flows in passageway 244 past check valve 246 to act upward on needle valve surface 248. The upward force opens needle valve 250 and fuel is discharged from orifice 252 against the bias of return spring 256. The piston 236 continues to move downward until the electric control 212 solenoid is de-energized, causing the poppet valve 210 to return to the lower seat 214 under the force of spring 220, blocking oil flow. The plunger return spring 232 then returns the piston 236 and plunger 228 to their initial upward inactive positions as depicted in FIG. 4. As the plunger 228 returns, the plunger 228 draws replenishing fuel into the fuel chamber 230 across ball check valve 242.
The nozzle 206 is typical of other diesel fuel system nozzles. The valve-closed-orifice style is shown, although a mini-sac version of the tip is also available. Fuel is supplied to the nozzle orifice 252 through internal passages. As fuel pressure increases, the nozzle needle 250 lifts from the lower seat 254 (as described below) allowing injection to occur. As fuel pressure decreases at the end of injection, the spring 256 returns the needle 250 to its closed position seated on the lower seat 254.
The fuel injector 200 uses the hydraulic energy of pressurized actuating fluid, in this case engine oil, to cause injection. The pressure of the incoming oil controls the downward speed of the intensifier piston 236 and plunger 228 movement, and therefore, the rate of fuel injection. The amount of fuel injected is determined by the duration of a signal keeping the electric control 212 solenoid energized. As long as the solenoid is energized and the poppet valve 210 is off its seat, the actuating fluid continues to push down the intensifier piston 236 and plunger 228 until the intensifier piston 236 reaches the bottom of its bore.
A similar hydraulically-actuated unit injector 200 is described in SAE paper No. 1999-01-0196, xe2x80x9cApplication of Digital Valve Technology to Diesel Fuel Injectionxe2x80x9d and U.S. Pat. No. 5,720,261. In this injector, the poppet control valve 202 of the HEUI injector has been replaced by a spool type digital control valve which is controlled by two solenoid coils, the valve spool being the armature.
In either case, there is a need for delivery of the high pressure volume of actuating fluid to the fuel injector in order to effect the fuel injection event. Actuating fluid delivery must be accomplished while allowing for assembly and part tolerance stack-ups and relative mechanical motion existing between the apparatus delivering the actuating fluid and the fuel injector. Tolerance stack-ups impose a considerable constraint on the design of any apparatus for delivering actuating fluid to a fuel injector. The injector, cylinder head, actuating fluid rail, and the connecting mechanism between the rail and the injector all have tolerances associated with them. Further, the connection between the rail and the injector must accommodate mechanical and thermal motion between the rail and the injector, the hydraulic load tolerance of the injector and the performance requirements of the injector. A desirable delivery mechanism is one that imposes no stress forces on the injector as a result of the aforementioned tolerances and of the aforementioned relative motion. The delivery mechanism should additionally be easily connectable to the injector.
U.S. Pat. No. 4,996,962, issued Mar. 5, 1991, discloses a fuel delivery rail assembly. The ""962 assembly uses sockets affixed to the tops of the fuel injectors. Plastic rail tubes extending between the sockets provide flexible engagements. The ""962 patent asserts that with such flexible engagements there is no need of strict limitation about a dimensional accuracy or geometrical orientation of the parts. It should be noted that while it is claimed that the flexible plastic rail tubes solve some of the problems sought to be solved by the present invention, there is no structure or teaching in the ""962 patent that relates to the present invention.
The actuating fluid delivery system of the present invention substantially meets the aforementioned needs of the industry. The connector assembly of the present invention that extends between the rail assembly and the fuel injector accommodates the aforementioned tolerances by being movable in three dimensions. Further, after installation, relative motion existing between the rail assembly and the fuel injector is further accommodated by the ability of the connector assembly to accommodate such motion by being shiftable in three dimensions and is rotatable at is least about a longitudinal axis, such rotation setting up the condition under which shifting in a plane disposed orthogonally with respect to the longitudinal axis may occur. The shifting does not occur unless there is the rotation and once rotation occurs, there is shifting. Additionally, the present invention provides for an exceedingly short path for the actuating fluid to travel from the rail assembly to the fuel injector. In the present invention, it is desirable that the L/D2 ratio for the connector assembly be less than one. The present invention is less than 70 mm in length and satisfies the aforementioned L/D2 ratio. Further, the connector assembly of the actuating fluid delivery system of the present invention is disposable in the limited space defined between the rocker arms of the head of the internal combustion engine.
The present invention is a fluid delivery system for delivering a supply of a fluid from a fluid source to a fuel injector and includes a rail for conveying a fluid, the rail being positionable proximate the fuel injector. The rail has a fluid passageway defined therein, the fluid passageway being in fluid communication with the source of fluid. A connector is in fluid communication with both the rail and with the fuel injector for fluidly connecting the rail to the fuel injector. The connector is moveable in three axes for accommodating static tolerances existing between the rail and the fuel injector and for accommodating dynamic relative motion between the rail and the fuel injector such that stresses imposed on the fuel injector resulting from being fluidly connected to the rail are substantially eliminated.